Safety switch for stopping mill when one ingredient supply is exhausted



July 16. 1968 R. F. SKELTON ETAL 3,393,280

SAFETY SWITCH FOR STOPPING MILL WHEN ONE INGREDIENT SUPPLY IS EXHAUSTED Filed Jan. 5. 1967 United States Patent M 3,393,280 SAFETY SWITCH FOR STOPPING MILL WHEN ONE INGREDIENT SUPPLY IS EXHAUSTED Robert F. Skelton, Blutfton, and Clyde R. Barnes, Ossian,

Ind., assignors to Mix-Mill, Inc., Bluifton, Ind., a corporation of Indiana Filed Jan. 3, 1967, Ser. No. 606,654 Claims. (Cl. 200-61.21)

ABSTRACT OF THE DISCLOSURE A group of ingredient bins are provided with a common safety shut-off including a plate which lies flat against the side of each filled bin, which is counterweighted to rise from the side of the empty bin. The counterweight is provided with a cam surface engaging a bell crank extending past all of the bins. The crank turns a cam to actuate a switch through a lever with an adjustable fulcrum, biased against the cam. When any bin is empty the switch is actuated to stop all mechanism dependent on receiving material from the bin.

Background '0) the invention A wide array of diaphragm switches, paddle switches, and the like have been tried in an effort to afford a simple and reliable switch which will disable a mechanism when one of a plurality of ingredient hoppers is empty. An example is a farm feed mixing device in which the hoppers are filled from respective storage areas by conveying devices. If the parent supply of any material is exhausted an incorrect mixture will result unless the machine is stopped. Prior art devices for the purpose are complex and are subject to vibration from the machine, which induces false operation or failure of the safety switch. The present mechanism is simple and inexpensive and is not subject to actuation or jamming by vibration. It operates with great precision and is readily adjusted.

Summary of the invention The invention consists of hanging identical counterweighted plates on the edges of respective ingredient hoppers, the weights being so related to the plates that when the hopper is empty the plate stands at an angle to the side of the hopper, the plate being arranged to lie flat on the wall of the hopper when the ingredient normally contained in the hopper presses against it. The counterweight portion of the plate is provided with a cam surface, and a common bell crank underlies all of said cam surfaces on the respective plates. The bell crank is provided with a cam on its end which is held to the bell crank with a set screw for adjustability. The cam operates a switch actuating lever which is spring biased toward the cam and which has a fulcrum portion resting on a screw for adjustment of the fulcrum point.

Drawings FIG. 1 is a fragmentary top plan view of a series of storage bins, showing the device of my invention applied thereto.

FIG. 2 is a fragmentary cross-sectional view taken on line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view taken on line 3,3 of FIG. 1.

Description of the invention In the drawings, a series of respective ingredient bins or hoppers designated 10, a, 10b, etc. Each hopper is provided with at least one sloping wall 11. A plate 12 is so formed as to lie fiat against side 11 and is bent at 13 to provide an apex or pivot which rests on the top 3,393,280 Patented July 16, 1968 margin of wall 11. It then is bent at 14 to form a curved ramp or cam surface, after which it extends outwardly to support a counterweight 15.

Underlying ramp portion 14 of each plate is the offset portion 20 of a bell crank. One end 21 of the bell crank is journaled in a switch box 22 which fully encloses the switch and switch actuating mechanism, to protect them from the dust of the ingredients which are stored in bins or hoppers 10, 10a, etc.

The other end of hell crank 20 is coaxial with end 21 and is merely journaled conventionally in a hole in a bracket (not shown).

Switch box 22 encloses a switch 23 provided with a lever 24 with which it is actuated. It is preferably of the normally closed type and is incorporated in a control circuit which stops the mechanism for withdrawing ingredients from bins 10, 10a, 10b, etc., when the switch is actuated. Of course, the switch may also serve to actuate an alarm to warn the operator of the empty bin, and to turn off all associated mechanisms, if desired.

The end 21 of bell crank 20 within box 22 is provided at its end with a cam 30 held with a set screw 31, so that the position of the high point of the cam may be adjusted.

' A cam follower arm 32 has a portion 33 which serves as a fulcrum, a central portion 34 at right angles to portion 33, and a terminal portion 35 which serves to actuate switch arm 24. A spring 36 biases the cam follower 32 toward the cam 30, insuring that it will make firm contact with the cam. The two-point contact stabilizes the device. A fulcrum adjusting screw 37 bears on fulcrum portion 33 of the cam follower 32 and is locked in place with a jam nut 38.

In operation, plate 12 hangs by apex 13 on the rim 11' of each hopper 10, 10a, 10]), etc., and is supported by counterweight 15 in a position spaced from wall 11 as shown in FIG. 3 as long as the bin or hopper is empty. When material 40 enters the hopper it pushes plate 12 against wall 11, and spring 36 and arm 32 pull the bell crank 20 to a position in which switch 23 is not actuated.

Should any one of bins 10, 10a, 10b, etc. become empty, the counterweight 15 of the plate 12 in that bin will pull the plate 12 away from wall 11 of the bin. Cam surface 14 will engage bell crank 20 and force it toward the wall 11 of the bin, rotating cam 30, The rotation of cam 30 moves cam follower 32 away from the end of shaft 21 of the bell crank 20 about screw 32 as a fulcrum. The outer end 35 of cam follower depresses arm 24 of switch 23, actuating the switch to stop the mechanism associated with the bins or give an alarm or both. If desired, switch 23 may also actuate a device to fill the bin, but it is contemplated that this device will be used in conjunction with other devices which normally maintain the bin in filled condition if there is any supply of the material forfilling the particular bin. In that type of mechanism, the fact that the bin is empty indicates that there is no supply of the particular ingredient to enter the bin (or that a malfunction has occurred) and accordingly the circuit is arranged to stop the entire mechan-ism.

Iclaim:

1. The combination of a series of bins for retaining separate ingredients, each of said bins being provided with a sloping side having a horizontal upper margin, the upper margins of the respective bins being aligned, with the improvement comprising a bell crank having an end on which the bell crank is journaled and an offset portion extending parallel to said aligned edges of said bins, a switch, switch actuating means on said bell crank, and a series of bell crank actuating members each comprising a plate adapted to lie against said sloping wall of said bin in one position, said plate having a central pivot at the top of said bin, a cam surface on said plate on the other side of said pivot from the portion of said plate adapted to lie against the wall of the bin, and a counterweight beyond sa-id cam surface from said pivot, each cam surface being adjacent the olfset portion of said bell crank, means biasing said bell crank toward a position in which said switch is not actuated by said switch actuating means, the counterweight being at such a distance from said pivot that when said bin is empty said plate is suspended with the portion adapted to lie against the wall of said bin extending at an angle to said Wall and said cam displaces said bell crank against said bias to a position in which said switch actuating means actuates said switch, the supplying of material to said bin being effective to displace said plate to lie against the wall of said bin and release said bell crank to move in response to said biasing means to a position in which said switch is not actuated by said switch actuating means.

2. The device of claim 1 in which said switch actuating means includes a cam on the journal end of said bell crank, a cam follower having a switch actuating arm and angularly related portions touching said cam, a fulcrum bearing on the end of one of said angularly related portions, said fulcrum means being adjustable toward and away from said cam.

3. The device of claim 2 in which said biasing means is a spring extending from said cam follower to a fixed part and arranged to exert tension on said cam follower toward said cam and the journal portion of said bell crank.

4. The device of claim 1 in which said pivot comprises a bend in said plate forming an apex, said apex being supported on the margin of the said wall of said bin.

5. The device of claim 1 in which said switch actuating means includes a cam on the journal end of said bell crank, a cam follow-er having a switch actuating arm and angularly related portions touching said cam, a fulcrum bearing on the end of one of said angularly related portions, said fulcrum means being adjustable toward and away from said cam, said biasing means being a spring extending from said cam follower to a fixed part and arranged to exert tension on said cam follower toward said cam and the journal portion of said bell crank, said pivot comprising a bend in said plate forming an apex, said apex being supported on the margin of the said wall of said bin.

References Cited UNITED STATES PATENTS 1,608,814 2/1925 Rioux 2006l.2

BERNARD A. GILHEANY, Primary Examiner.

F. BELL, Assistant Examiner. 

